Choices, Choices: What Do You Need in a WAP?

Wireless LANs are proliferating at a truly astonishing rate. Dell'Oro Group, a US-based research house, predicts the WLAN market will have tripled from 2003 to 2007, while Gartner predicts it will grow at a compound annual rate of 15 percent for the next two years to become a $4 billion market by 2007. From almost zero penetration five years ago, Gartner estimates that today about half of all U.S. SMBs have a wireless LAN somewhere in the organization.

For anyone starting to roll out a wireless LAN the biggest decision is whether to use fat APs, or a combination of thin APs and wireless switches.

Wireless access points (APs) are a key part of any WLAN as they provide wireless connectivity between the network and individual wireless clients. And not surprisingly, there's no shortage of vendors who supply them.

The biggest vendor by revenue in the enterprise space is Cisco, followed by Symbol Technologies, Airespace (which is in the process of being acquired by Cisco) Proxim, and 3Com, according to U.S.-based research house Synergy. Other well known hardware vendors with small market shares include Avaya, Alcatel, and Nortel.

All APs provide network access, but there are a variety of ways they achieve that and differentiate themselves from each other.

The original 802.11b (define) Wi-Fi standard has rapidly been replaced by the faster but backward compatible 802.11g standard, and nearly all APs offer b/g connectivity. The 11b standard is still important as many clients only have 11b access, but newer equipment is nearly always 11g, so a mixed 11b/g AP is the norm.

Rollout of APs using the newer 5GHz 802.11a standard has been slowed because few devices are 11a compliant, but some Centrino laptops now support the standard, so 11a is beginning to pick up. "When we receive an RFP, we nearly always find that nowadays companies are asking for 802.11a support, especially larger organizations, even if they don't intend to use it straight away," says Thomas Boehle, a senior networking consultant at 3Com.

For this reason many vendors supply APs that can work in either 2.4GHz 11b/g mode or the 5GHz 11a mode, or with the option to add a card that enables 11a functionality. Increasingly, vendors are also offering APs that can work in b/g and a mode simultaneously. "There are a lot of advantages to this," says Anthony Fulgoni, a sales manager at Proxim. "You can use both modes at the same time, and as you have two radios you can increase the aggregate capacity to 42 megs. Or you can use the 11b/g mode to communicate with clients, and use the 11a radio as a point to point backhaul system – if you are in a temporary location over the road from your main office you could do bridging in 11a."

The 11a standard has other benefits: There is effectively more spectrum available with more non-overlapping channels, so in a high density office environment this makes it far easier to implement many APs on different channels in close proximity to each other.

Security, security, security
While consumer grade APs often rely on MAC address (define) filtering to restrict network access to known client machines, enterprise APs need more sophisticated RADIUS authentication (define) , as well as heavy duty encryption such as WPA2 (define) . This goes further than the earlier WPA by adding AES (Advanced Encryption System) key support using CCMP (Counter Mode CBC-MAC Protocol). Some APs have hardware encryption add-ons to ensure performance doesn't degrade while encryption is being carried out. "From a protocol standpoint, almost all known vulnerabilities have been dealt with," says Abner Germanow, enterprise networking program manager at U.S.-based analyst IDC. But there's still work to be done in terms of making encryption easy to use and turned on by default. Over the next year or so we will see people taking protocols and building software around them to make them easier to use."

Some APs – usually through management software systems – also support rogue AP detection. These work by scanning the area for other APs with unrecognized MAC addresses, and reporting any that are detected so they can be investigated.

Fat or Thin APs?
In addition to fully featured – and relatively expensive – APs, some vendors including Symbol, Airespace, Aruba and 3Com offer "thin" APs with a much smaller software stack. These are connected to a wireless switch – a LAN-connected device administrators can log into to manage and configure all the APs centrally. The benefit of this approach is that as the AP hardware itself is (marginally) cheaper, in large deployments the cost savings can be an important consideration. The wireless switches themselves enforce network policies, network security and Quality of Service rules for applications such as IP telephony. Some proponents of thin APs argue that a wireless switch makes large numbers of APs far easier to manage, although management software suites that enable fat clients to be managed centrally are available from some vendors – notably Cisco with its Structured Wireless-Aware Network (SWAN) strategy, which builds "wireless awareness" into various parts of its network infrastructure.

Voice over WLAN
In the near future, many companies are likely to investigate the possibility of replacing wired or DECT wireless telephone systems with wireless IP telephony. The topline benefit, if it can be done effectively, is that enterprises will have just one data network – rather than separate phone and data networks – to maintain. There are some difficult hurdles still to be overcome – like how to roam easily between different subnets, and how to ensure seamless coverage in places like stairwells and elevators, which are not typically covered by wireless LANs – but many vendors are working on this. At the moment, if you want anything approaching a working Voice over WLAN system, it's likely your IP phones, APs and proprietary software will all have to come from a single vendor.

Taking a further step towards fixed/mobile convergence, some vendors, including Proxim and 3Com, are also looking at the possibility of integrating GSM cellphone capabilities into APs so calls can roam between the WLAN and standard GSM networks. With combined GSM/VoIP handsets executives could start an IP call in the office and continue on the GSM network as he or she walked out on to the street.

WiMax
The 802.16 standard known as WiMax (define), with a range of miles rather than feet, looks likely to have an impact on AP vendors over the course of the next 12 months or so. Initially business customers might use it as a WAN link between offices, but as prices come down it's likely a few 802.16 APs could provide campus-wide connectivity to organizations that are geographically spread out, or even to enable employees to work from home while remaining connected to the enterprise network.

Which vendor?
Choosing an AP vendor is not a trivial matter, and given the sheer quantity of them competing for business the task can be deceptively hard.

For anyone starting to roll out a wireless LAN the biggest decision is whether to use fat APs, or a combination of thin APs and wireless switches. This will depend on the size and future scaling requirements of the implementation, and once this decision has been made then factors including manageability, security and availability of additional services like voice will come to the fore. Cost is obviously also important, but in this cut-throat part of the networking business competition is fierce, and for the foreseeable future prices look set to continue falling sharply. If you can't afford what you need now, the chances are you will be able to in a couple of months.